We can read, create, and delete sessions over a single $_SESSION global array. The only important issue is that we must write the session_start() function at the top of each page before we start using session, which prepares the session event and is essential.
On some servers, session usage is always on automatically, and if you try to write session_start() on open servers, it will fail. In this case there is no need to use this function.
<?php
session_start();
$_SESSION['message'] = 'Hello world!';
?>
Above we started a session,added a key message inside the global array $_SESSION with the value Hello world!. So I’ve created a session called message and its value is Hello world!.
This value will be sent back to every page he visits unless the browser is closed and the user will be able to remember his previous actions, such as username or password.